1. Field of Invention
This invention relates generally to the field of placing or siting detectors within a facility and, more particularly, to a method, system and article of manufacture to place one or more detectors in a facility with a view towards maximizing the detectability of contaminants released within the facility.
2. Description of the Prior Art
The malevolent release of biological, chemical or other hazardous materials inside a large, public facility is considered by many to be a serious threat. When released in the confines of a facility, even very small amounts of a biological, chemical or other hazardous agent (collectively referred to as “agent”) can create a substantial risk.
Attacks using agents are likely to be covert. Therefore, in the absence of a detector system within the facility capable of sensing the agent, the first evidence of the attack may come days after the actual release when patients start flooding emergency rooms or other medical care providers. Early detection of agents allows effective treatment of pre-symptomatic exposed patients.
One aspect of protecting an airport, transportation node or other facility from malevolent release of an agent (or multiple agents) is the deployment of a detection system within the facility. An important aspect of the design and installation of such a detector system is to place or site the detectors or sensors at locations within the facility so as to effectively detect agents. Advantageously siting detectors for effective sensing of agents is one objective of the present invention.
Detectors can be expensive, and the cost of a detector system is typically directly related to the number of detectors in operation. Under such circumstances, there is a strong incentive to determine the smallest number of detectors that provides the desired detection capabilities within the facility. However, whether or not detector cost is a major concern in the design of a detector system, it is advantageous to select the locations for placing any finite number of detectors within a facility with a view towards maximizing (or improving) the detectability of agents released within the facility. This is another objective of the present invention.
Conventionally, when deploying a detector system in a facility including one, two or a very few detectors, the deployment location is typically based on a simple facility walkthrough and a subjective determination of detector siting. Using a walkthrough approach, it is possible that a detector will be placed at a location, site j, such that it will not be able to detect a release occurring at location i. In addition, employing this walkthrough approach may result in the number of detectors and the location of the detectors not providing the desired coverage or an acceptable level of coverage.
Typical techniques for siting detectors in facilities focus on maximizing the ability to calculate the source of a release from information obtained by detectors in the facility, for example, as described by F. Gelbard, J. E. Brockmann, and K. K. Murata in “Sensor Analysis Software (SAS): An Algorithm for Determining Airborne Agent Concentrations Throughout a Large Multi-Room Building”. Technical Report SAND 99-1945, Sandia National Laboratories, Albuquerque N. Mex., August 1999, and by F. Gelbard, J. E. Brockmann, K. K. Murata, and W. E. Hart in “An Algorithm for Locating Sensors in a Large Multi-Room Building”. Technical Report SAND 2000-0851, Sandia National Laboratories, Albuquerque N. Mex., May 2000. Dynamically placing visual sensors such as TV cameras to achieve visual coverage of a three-dimensional volume is described by Arpa et al US Patent Publication No. 2005/0002662.
However, a different situation is presented when, as here, it is desired to place detectors so as to detect a minimum or near minimum release of agent, in contrast with techniques focused on siting detectors so as to determine the source of release. When it is desired to identify the source of agent release, the available number of detectors may be placed in such a way that the resulting detector system will be unable to detect a release from all realistic release points, i. Hence, one objective of the present invention is to site detectors at locations j within a facility so as to achieve acceptable (ideally, optimal) detection of the smallest feasible release of agents at any feasible release location i within the facility. Thus, there is a need in the art for a technique to site detectors within a facility which considers the minimum agent released that the system is capable of detecting from all feasible release locations.